text: #include <stdio.h>
  
  void f1 (void) { printf("%i\n", 1); }
  void f2 (void) { printf("%i\n", 2); }
  void f3 (void) { printf("%i\n", 3); }
  void f4 (void) { printf("%i\n", 4); }
  void f5 (void) { printf("%i\n", 5); }
  void f6 (void) { printf("%i\n", 6); }
  void f7 (void) { printf("%i\n", 7); }
  void f8 (void) { printf("%i\n", 8); }
  void f9 (void) { printf("%i\n", 9); }
  
  typedef void(*void_fp)(void);
  
  // There is a basic check that excludes all functions that aren't used anywhere
  // This ensures that check can't work in this example
  const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
  
  typedef struct fp_cc
  {
    int x;
    void_fp fp;
  } fp_cc;
  
  
  
  void func()
  {
    const fp_cc container_container = { .fp = f2, .x = 4 };
  
    const fp_cc * const container_pointer = &container_container;
  
    fp_cc* container_pointer_modifier = (fp_cc*) container_pointer;
    container_pointer_modifier->fp = f4;
  
    // Illegal:
    // container_container.container = &f4;
  
    container_pointer->fp();
  }
  
  int main()
  {
    func();
  }
  